"Sensitivity analysis (SA) is the study of how the variation in the output of a model (numerical or otherwise) can be apportioned, qualitatively or quantitatively, to different sources of variation, and of how the given model depends upon the information fed into it. On this basis, we contend that SA is a prerequisite for model building in any setting, be it diagnostic or prognostic, and in any field where models are used."--P. [3].